Common Lisp is in the same category as a FP-ish language but still mostly used in a mutable OO fashion. We have a library called FSET written in CL to add persi

Common Lisp is in the same category as a FP-ish language but still mostly used in a mutable OO fashion. We have a library called FSET written in CL to add persistent data structures and convenient syntax for them to the language. I don't know how powerful ruby meta-programming is, but I imagine it isn't as easy to do(like add a syntax for persistent maps that is as convenient as the built in one). Not to mention that ruby has a reputation for much worse performance than CL, so you'll likely have to use FFI and write most of it in C. As for clojure, I think they are all implemented in java, but I haven't been following clojure development in two years, so maybe with protocols they moved them(or could) to clojure? I don't know.